NAME
Class::Data::Inheritable - Inheritable, overridable class data
SYNOPSIS
package Stuff;
use base qw(Class::Data::Inheritable);
# Set up DataFile as inheritable class data.
Stuff->mk_classdata('DataFile');
# Declare the location of the data file for this class.
Stuff->DataFile('/etc/stuff/data');
DESCRIPTION
Class::Data::Inheritable is for creating accessor/mutators to class
data. That is, if you want to store something about your class as a
whole (instead of about a single object). This data is then inherited by
your subclasses and can be overriden.
For example:
Pere::Ubu->mk_classdata('Suitcase');
will generate the method Suitcase() in the class Pere::Ubu.
This new method can be used to get and set a piece of class data.
Pere::Ubu->Suitcase('Red');
$suitcase = Pere::Ubu->Suitcase;
The interesting part happens when a class inherits from Pere::Ubu:
package Raygun;
use base qw(Pere::Ubu);
# Raygun's suitcase is Red.
$suitcase = Raygun->Suitcase;
Raygun inherits its Suitcase class data from Pere::Ubu.
Inheritance of class data works analogous to method inheritance. As long
as Raygun does not "override" its inherited class data (by using
Suitcase() to set a new value) it will continue to use whatever is set
in Pere::Ubu and inherit further changes:
# Both Raygun's and Pere::Ubu's suitcases are now Blue
Pere::Ubu->Suitcase('Blue');
However, should Raygun decide to set its own Suitcase() it has now
"overridden" Pere::Ubu and is on its own, just like if it had overriden
a method:
# Raygun has an orange suitcase, Pere::Ubu's is still Blue.
Raygun->Suitcase('Orange');
Now that Raygun has overridden Pere::Ubu futher changes by Pere::Ubu no
longer effect Raygun.
# Raygun still has an orange suitcase, but Pere::Ubu is using Samsonite.
Pere::Ubu->Suitcase('Samsonite');
Methods
mk_classdata
Class->mk_classdata($data_accessor_name);
This is a class method used to declare new class data accessors. A new
accessor will be created in the Class using the name from
$data_accessor_name.
To facilitate overriding, mk_classdata creates an alias to the accessor,
_field_accessor(). So Suitcase() would have an alias
_Suitcase_accessor() that does the exact same thing as Suitcase(). This
is useful if you want to alter the behavior of a single accessor yet
still get the benefits of inheritable class data. For example.
sub Suitcase {
my($self) = shift;
warn "Fashion tragedy" if @_ and $_[0] eq 'Plaid';
$self->_Suitcase_accessor(@_);
}
AUTHOR
Original code by Damian Conway.
Maintained by Michael G Schwern until September 2005.
Now maintained by Tony Bowden.
BUGS and QUERIES
Please direct all correspondence regarding this module to:
bug-Bit-Vector-Minimal@rt.cpan.org
COPYRIGHT and LICENSE
Copyright (c) 2000-2005, Damian Conway and Michael G Schwern. All Rights
Reserved.
This module is free software. It may be used, redistributed and/or
modified under the terms of the Perl Artistic License (see
http://www.perl.com/perl/misc/Artistic.html)
SEE ALSO
perltootc has a very elaborate discussion of class data in Perl.